Process for refining wood rosin



Patented Dec. 2 9, 1942 PROCESS FOR REFINING WOOD ROSIN William N.Traylor, Hattiesburg, Miss, assignor to Hercules Powder Company,Wilmington, Del., a corporation oi Delaware No Drawing.

Application April 10, 1940,

Serial No. 328,867

12 Claims.

This invention relates to a process for refining rosin and moreparticularly relates to a process for refining wood rosin.

It is well known that wood rosin obtained by extraction of pine wood,for example with a suitable solvent, is dark in color due to thepresence of color bodies. Many methods have been proposed in the art forthe removal of color bodies from the rosin to produce rosins of palergrades. These methods, however, have been open to one objection oranother. Thus, while some methods have given a certain degree ofrefinement, they have not always been successful in producing a rosin ofthe degree of refinement required for many uses. Furthermore, in thoseprocesses where light-colored products have been made, it has beennecessary to subject the rosin to treatments which generally result in alow yield of the refined rosin, and, consequently, a relatively highcost per unit.

It is an object of this invention to provide an improved process forrefining wood -rosin.

It is a further object to provide an improved process for refining woodrosin which is extremely simple and economical.

It is another object to provide a process for refining wood rosin inwhich ordinary plant equipment may be used.

It is still another object to provide a process for refining wood rosinin which the properties, other than color, of the refined rosin aresubstantially unaltered from those of the unrefined original rosin.

It is a still further object to provide a process for refining woodrosin which will provide a refined product in a substantiallyquantitative yield based on the original rosin.

Other objects of the invention will appear hereinafter.

The above objects are accomplished in accordance with this invention bytreating wood rosin under ionizing conditions with an acid salt and ametal above hydrogen in the electromotive series. The treatment iscarried out under conditions which will provide intimate contact betweenthe rosin, the acid salt and the metal. As a result of the abovetreatment the color of the rosin becomes substantially lightened withpractically no loss in yield and no perceptible efiect on the otherphysical properties.

In accordance with the process of this invention the treatment may becarried out on the rosin in the molten condition or it may be carriedout on the rosin dissolved in a suitable organic solvent. After thetreatment of the rosin is completed, the rosin or the rosin solution mayI be washed to remove the water-soluble materials and filtered to removethe metal.

- been subjected to a previous refining process,

such as are well known in the art, may be used. If a very pale rosin isdesired, a wood rosin which has already undergone a refining-treatmentwill be preferred. Relatively pale rosins may be produced, however, fromwood rosins as dark as FF lOSln.

As solvents for the rosin, where the treatment is carried out on therosin in solution, any solvent for rosin which is itself inert in thetreatment may be employed. Among such solvents are, for

example, monocyclic aromatic hydrocarbons, such as benzol, toluol,xylol, etc.; petroleum hydrocarbons, such as gasoline, V. M. and P.naphtha, hexane, heptane, etc.; hydrogenated petroleum hydrocarbons,such as those known in the trade as "Solvesso solvents; and solventssuch as ethylene dichloride, carbon tetrachloride, cyclohexane,methylcyclohexane, etc. Where the treatment is carried out on the rosinin solution the concentration of the rosin in the solvent is notcritical and may be selected so as to provide adequate workability ofthe solution. Generally speaking, a concentration within the range ofabout 5% to about 95% by weight may be used, but preferably theconcentration will fall within the range of about 20% to about 50% byweight.

The acid salts which may be used in the process of this invention arethose which contain one or more replaceable hydrogen atoms, such as, forexample, sodium acid sulfate, potassium acid sulfate, monosodiumacidrphosphate, disodium acid phosphate, monopotassium acid phosphate,dipotassium acid phosphate, calcium acid phosphate, lithium acidphosphate, etc.

Any of the metals above hydrogen in the electromotive series may beemployed. It will be preferable, however, to use such metals which formsalts having no appreciable discoloring action on rosin. The metals areused preferably, though not necessarily, in a finely divided form. Useof metals, as, for example, cadmium, aluminum, manganese, tin and zincis very desirable. Zinc in the form of zinc dust, mossy zinc or zincpowder is particularly well adapted to the process.

Having described the improved process of refining rosin in accordancewith this invention in broad terms, a more detailed description of theprocess will now be given. As stated above, the treatmentmay be carriedout on the rosin in molten condition or dissolved in a solvent. Ineither case, it is desirable that at least a small amount of water or ofsome other ionizing solvent be present to accelerate the refiningaction. Thus the acid salt may be used in the form of a hydrate,.if itforms one, or in the form of an aqueous solution. Sodium acid sulfate inthe form of its monohydrate is particularly desirable. Alternatively, asmall amount of water or other ionizing solvent may be added. An aqueoussolution containing from about per cent of the acid salt to a saturatedsolution of the salt at the temperature employed may be used.

It will be understood that the acid salt and the metal above hydrogen inthe electromotive series are both in contact with the rosin during thetreatment. To provide satisfactory contact of the ac d salt and metalwith the rosin it will be desirable to employ vigorous agitation sincethe refining action will be appreciably accelerated.

The speed with which the rosin becomes refined in accordance with theprocess of the invention is dependent on the temperature employed in thetreatment. While the treatment may be carried out at room temperaturewith ros n d ssolved in a solvent, the rate of refining is rather slowfor p actical purposes. It is preferable to carry out the treatment atelevated temperatures and temperatures as high as 160 C. have been foundto be satisfactory. A temperature within the range of about 70 C. toabout 125 C. has been found particularly satisfactory. When carrying outthe treatment on the rosin in solution it is convenient to operate atthe reflux temperature of the solution. Where the treatment is to becarried out above the normal boiling point of the solvent, use ofsuperatmospheric pressure is resorted to. The pressures employed are inno way limiting on the process and the equ pment employed will generallydetermine the maximum pressure which is practical.

The time of treatment of the rosin in accordance with the process of theinvention may be varied to provide the result desired. The timenecessary to provide satisfactory refining of the rosin will bedependent on such factors as the amount of color bodies present in therosin, the

temperature of treatment, the amount of acid salt employed, as well asothers. For this reason it is impossible to state any definite timenecessary, except in relation to a given set of conditions. serve toillustrate the time of treatment which may be used in each particularcase.

The amount of acid salt used may vary over a wide range, depending uponsuch factors as the particular acid salt used, the degree of refiningdesired, the particular conditions of treatment, as well as otherfactors. Considering the acid salt on an anhydrous basis, for example,ratios of wood rosin to acid salt as high as to 1 on a weight basis havebeen used. In general, however, ratios varying between 10 of rosin to 1of acid salt down to 1 of rosin to 1 or more of acid The examples whichfollow will.

salt are desirable. A preferred ratio is approximately 1 of acid salt to2 of wood rosin.

The amount of metal above hydrogen in the electromotive series used isnot particularly critical. It will be desirable, however, to have anamount of such metal present which will be an excess over thetheoretical amount required to react with the acid salt present.

As illustrative of the improved process of refining wood rosin inaccordance with this invention the examples appearing below are cited astypical of the various embodiments. The colors shown in the examples arethe Lovibond glass colors measured on cubes of the rosins.

Example 1 Two hundred parts by weight of a 50% solution of K wood rosin,(40 Amber+1.5 Red) in benzol were refiuxed for one hour at a temperatureof TO-73 C. with 30 parts by weight of sodium acid sulfate monohydrate(NaSCrHzO) and 20 parts by weight of zinc dust. The solution was thenfiltered, diluted to a 20% rosin concentration with fresh benzol, washedthree times with water, filtered, and the rosin-containing solutionheated to distill off the benzol, the last of the solvent being removedwhile sparging with carbon dioxide. The color of the refined rosin was11 Amber, corresponding to a grade of X. The yield was substantiallyquantitative.

Example 2 Five hundred parts by weight of a 20% solution of K wood rosin(40 Amber+1.5 Red) in gasoline were heated in a Monel metal autoclavewith 250 parts by weight of a 30% a"ueous solution of sodium acidsulfate and 50 parts by weight of zinc dust. The contents of theautoclave were heated to a temperature of 158 C. with agitation, thepressure rising to 70 lbs/sq. inch. After allowing the autoclave tocool, the rosin-containing solution was removed and washed with waterseveral times, filtered, and the solution then heated to distill off thegasoline, the last of the gasoline being removed while sparging withcarbon dioxide. The color of the refined rosin was 22 Amber, whichcorresponds to a WG grade. The yield was substantially equal to therosin treated.

Example 3 Grade U. 8. standard tim Lovibond color Original FF rosin FRefined rosin M Example 4 Three thousand parts by weight of a 25%solution of FF wood rosin in benzol, 1000 parts by weight of a35%aqueous solution of sodium acid sulfate and parts by weight of zincdust were heated together under vigorous agitation in an Grade Lovibondg fi; color 8rd type Original FF rosin 80A+3OR. F Reflnedrosin 40A+2.5R.K

Example Two hundred parts by weight of a 50% solution of FF wood rosinin benzol were refluxed for 25 minutes with 20 parts by weight of zincdust and 20 parts by weight of sodium acid sulfate monohydrate.Thereafter '300 parts by weight of benzol were added and the dilutedbenzol solution was washed with a 5% aqueous oxalic acid solution andthen with distilled water. The solution was filtered, the volatilecomponents distilled oil', the last thereof being removed while spargingwith carbon dioxide. The yield of refined rosin was 98.5% based on theweight of the FF rosin used. The improvement in color was as follows:

(ljrage Lovibond standcolor Md type Original FF rosin 80A+20R G Refinedrosin 38A M Example 6 Fifty parts by weight of M wood rosin weredissolved in 200 parts by weight of gasoline. This solution was refluxedwith 30 parts by weight of sodium acid sulfate monohydrate and 20 partsby weight of zinc dust for one hour.-

The refined rosin solution after cooling was then washed three timeswith water, filtered to remove the metal remaining and the rosin thenrecovered by distilling off the solvent, the final portions thereofbeing removed while sparging with carbon dioxide.- The refined rosin wasobtained in a yield of 98% based on the weight of M rosin A 50% benzolsolution of a crude wood rosin .having a color of about 80 Amber+300 Redwas prepared. Portions of 100 parts by weight each dioxide.

of this benzol solution were refluxed separately 7 for one hour eachwith the following acid salts and metals, the proportions being byweight.

acid sulfate monohydrate. 10 parts of aluminum and 10 parts of sodiumacid sulfate monohydrate. 10 parts of zinc and 10 parts of sodium acidsulfate monohydrate. 10 parts of zinc and 10 parts of potassium acidsulfate. 10 parts of zinc and 10 parts of primary 4 sodium acidphosphate. 10 parts of zinc and 10 parts of primary calcium acidphosphate. 10 parts of tin and 10 parts of sodium acid sulfatemonohydrate.

In each case the metal was present in divided form and in 4, 5 and 6 asmall amount of water was included.

After treatment in each of the above cases the refined rosin solutionwas diluted with 150 parts by weight of fresh benzol and was given threewater washes. Thereafter the solution was filtered, the volatileportions distilled off, the last thereof being removed while spargingwith carbon in each case was as follows:

Sample number Lovibond color amber+300 red. 80 amber-H00 red. 80amber+2l0 red. 80 amber+ 50 red. 80 arlglber+l50 red.

80 amher+l30 red. 80 amber-+210 red.

Example 8 acid sulfate monohydrate for one-half hour at a temperature ofto C. Thereafter the reaction mixture was allowed to cool and the rosinextracted with parts by weight of toluol. The rosin solution was thenfiltered through a bed of Filter-cel in order to remove small amounts ofdispersed zinc. The solvent was then removed under reduced pressure, therosin remaining graded M+ in color, which constitutes-an improvement of1 grades.

The process of refining wood rosin described in accordance with thisinvention may also be carried out as a continuous process. Thus, therosin solution inay, for example, be treated with the acid salt andmetal in a suitable vessel While the rosin solution is fed into thevessel continuously. The acid salt and metal may be replenished asnecessary in the reaction vessel. A continuous flow of refined rosinsolution may thus be pro ided from the reaction vessel.

The many advantages of my improved process of refining wood rosin willbe readily apparent from the above description and examples. The processis extremely simple and economical. The color improvement of rosinobtained is remarkable, particularly in view of the high yield ofrefined rosin obtainable. In previous methods of improving the color ofrosin a considerable loss in rosin has always been evident.

It is to be understood that the term "refining used throughout thisinvention refers particularly to the color improvement of the rosin and10 parts of magnesium and 10 parts of sodium The color of the refinedrosin obtained 7 not necessarily to a separation of the rosin intolight-colored and dark-colored fractions.

It will also be understood that the details and examples hereinbeforeset forth are illustrative only, and that the invention as broadlydescribed and claimed is in no way limited thereby.

What I claim and desire to protect by Letters Patent is:

1. A process for refining wood rosin which comprises treating wood rosinwith an acid salt prises treating wood rosin in molten form with an acidsalt and a metal above hydrogen in the electromotive series in thepresence of at least a small amount of water.

4. A process for refining wood rosin which comprises heating wood rosinwith an acid salt and a metal above hydrogen in the electromotive seriesin the presence of at least a small amount of water.

5. A process for refining wood rosin which comprises heating wood rosinwith an acid salt and a metal above hydrogen in the electromotive seriesat a temperature not in excess of about 160 C. in the presence of atleast a small amount of water.

6. A process for refining wood rosin which comprises treating wood rosindissolved in a suitable solvent with an acid salt and zinc in thepresence of at least a small amount of water.

'7. A process for refining wood rosin which comprises treating woodrosin dissolved in a suitable solvent with zinc and a hydrate of sodiumacid sulfate in the presence of at least a small amount of water.

8. A process for refining wood rosin which comprises treating wood rosindissolved in a suitable solvent with sodium acid sulfate monohydrate andzinc in the presence of at least a small amount of water.

9. A process for refining wood rosin which comprises treating wood rosindissolved in a suitable solvent with zinc and an aqueous solution ofsodium acid sulfate.

10. A process for refining wood rosin which comprises heating wood rosinwith an acid salt and a metal above hydrogen in the electromotive seriesat a temperature within the range of about 70 C. to about 125 C. in thepresence of at least a small amount of water.

11. A process for refining wood rosin which comprises heating wood rosinwith sodium acid sulfate and zinc at a temperature within the range ofabout 70 C. to about 125 C. in the presence of at least a small amountof water.

12. A process for refining wood rosin which comprises heating wood rosindissolved in a suitable solvent with sodium acid sulfate monohydrate andzinc at a temperature within the range of about 70 C. to about 125 C.

WILLIA N. TRAYLOR.

